Single-stage systems

The urea solution is evaporated in a two-stage system (99.8%) if the final product is prills, and a single-stage system (+95%) if granules are to be provided. 

A typical pictorial flow diagram for the ammonia system is given in Figure 11-14 for a single-stage system and in Figure 11-15 for a two-stage ammonia system. 

For purposes of our discussion here, we will primarily focus on the single-stage system, which is the simplest. The approaches presented here are appropriate for use in any of these screening systems, although establishment of activity criteria becomes more complicated in successive screens. Clearly, the use of multistage screens presents an opportunity to obtain increased benefits from the use of earlier (lower-order) screening data to modify subsequent screen performance and the activity criterion. 

Assess results Several methods can be applied to minimize the ozone consumption in combined processes of ozonation and biodegradation. For example, the different operational behavior of batch and continuous-flow systems, with the resulting differences in oxidation products, etc. has to be considered, as well as the fact that multi-stage systems for each treatment process may be of advantage over single stage systems. 

C. As a simplification, let us assume complete immiscibility of benzene and water. To accomplish this extraction in a single-stage system, one can set up an equation to calculate the concentration of benzoic acid in each of the streams produced. To do this, the value for the concentration of benzoic acid in the first extract [BzOH]e is obtained from the known equilibrium which must exist between the two streams of Eq. 10.36. This value is substituted into Eq. 10.37, which defines the balance of concentrations of benzoic acid which must exist between the incoming and outgoing streams. 

When pumping equipment is at the surface, the depth of wells and wellpoints that can be pumped is limited to the lift supplied by air pressure. In practice, because of equipment inefficiencies, gravity lifts seldom go above 15 feet. The use of a single stage system is shown in Figure 4.3. 

The employment of the one-through single-stage system and some devices for sanitary maintenance prolonged the sterilization interval and reduced the running cost. 

Fig 6 shows the single-stage system, which is referred to as plasma-driven catalysis [77]. In the PDC process, catalysts arc directly placed in the NTP reactor. These catalysts arc activated by NTP at low temperature region, where the thermal catalysis docs not occur. The shape of catalyst is cither of honeycomb, foam or pellet. In contrast to the PEC system, all reactions of gas-phase, surface and their interaction lake place simultaneously. In this sense, it is quite complicate to understand and optimize the chemical reactions in the PDC system. In an early USA patent, Henis proposed a PDC reactor for NO.r removal. Figure 7 shows the schematic diagram of the PDC reactor proposed by Henis [78], which is quite similar to those used in recent studies. The gases arc introduced to the reaction zone through the contact materials for heat transfer purpose. The catalysts listed in the patent are alumina, zirconium silicate, cobalt oxide, Thoria, activated carbon, molecular sieves, silica gel etc. 

In a single-stage system aU work required by a job or a customer is done by one service facility. However, this facihty may consist of a number of servers or machines in parallel, and system performance win depend on how jobs or customers are allocated to the machines or servers. 

Equation (2-111 is the operating equation, which for a single-stage system relates the conpositions of the two streams leaving the stage. Equation (2-111 can be rewritten in terms of either the fraction vaporized, f = V/F, or the fraction remaining liquid, q = L/F. 

The operating lines in Figure 13-9 are similar to those we found for binary flash distillatiom Both single-stage systems and cross-flow systems are arranged so that the two oudet streams are in equilibrium and on the operating line. This is not true of countercurrent systems. 

Except that this equation uses masses of raffinate and extract instead of flow rates, it is essentially the same as the continuous operating equation for a single-stage system (Eq. 113-191 with] = 1). Thus, the solution is identical to the continuous solution and can be obtained either graphically IFigures 13-9 and 13-101 or analytically Eq. 113-211 for linear isotherms with] = 1). 

C5. Single-stage systems (N = 1) can be designed as countercurrent systems, Figure 13-4. or as cross-flow systems, Figure 13-9. Develop the methods for both these designs. Which is easier If the system is dilute, how can the Kremser equation be used ... 

D18. Repeat Example 14-2 except for a single-stage system and unknown underflow product concentration. 

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